Foldable display device

ABSTRACT

A foldable display device assembly includes a rigid film having first and second sections spaced apart from each other, the rigid film being foldable about a folding axis disposed between the first and second sections of the rigid film; an adhesion structure having first and second adhesion sections spaced apart from each other, the first and second adhesion sections being disposed on the first and second sections of the rigid film, respectively; a lower flexible module disposed on the adhesion structure; a flexible display module disposed on the lower flexible module; and an upper flexible module disposed on the flexible display module.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No.16/353,336, filed on Mar. 14, 2019, and claims from and the benefit ofKorean Patent Application No. 10-2018-0048776, filed on Apr. 26, 2018,which is hereby incorporated by reference for all purposes as if fullyset forth herein.

BACKGROUND Field

Embodiments of the invention relate generally to a light-emittingdisplay device, and, more specifically, to a foldable display devicecapable of being switched between a folded state and an unfolded state.

Discussion of the Background

Examples of a display device include an organic light-emitting diode(OLED) display device and a liquid crystal display (LCD) device.

Portable electronic devices usually include a display device to displayimages to a user. Portable electronic devices having a relatively smallsize, but having a relatively large display screen, have become popular,and the development of foldable or bendable display devices capable ofbeing folded or unfolded to provide a large screen when in use isunderway. Heretofore, folding of display devices has resulted in curvedsections of the display that degrade display quality.

The above information disclosed in this Background section is only forunderstanding of the background of the inventive concepts, and,therefore, it may contain information that does not constitute priorart.

SUMMARY

Display devices constructed according to illustrative implementations ofthe invention provide a foldable display device capable of reducing orpreventing the degradation of display quality.

For example, the foldable display device may include a display moduleand one or flexible films to position the neutral plane of the foldabledisplay device at a particular location in the display module or in alayer of the display module, such as where driving transistors areformed, and/or may include one or more rigid films to maintain thedisplay module in a relatively flat configuration even when an externalforce is applied.

Additional features of the inventive concepts will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the inventive concepts.

According to an embodiment of the invention, a foldable display deviceassembly may comprise a rigid film, a first double-sided adhesive film,a lower flexible module, a second double-sided adhesive film, a flexibledisplay module, a third double-sided adhesive film, and an upperflexible. The rigid film may have first and second sections betweenwhich a spacer having a first width is located. As one example, aportion of the first section and a portion of the second section may beconnected to each other and the space may be located between theremaining portion of the first section and the remaining portion of thesecond section. As another example, the first and second sections may beseparated from each other. The rigid film may be foldable about afolding axis disposed between the first and second sections. The firstdouble-sided adhesive film may be disposed on the rigid film. The lowerflexible module may be disposed on the first double-sided adhesive film.The second double-sided adhesive film may be disposed on the lowerflexible module. The flexible display module may be disposed on thesecond double-sided adhesive film. The flexible display module may havean electroluminescent unit. The third double-sided adhesive film may bedisposed on the flexible display module. The upper flexible module maybe disposed on the third double-sided adhesive film.

The first double-sided adhesive film may extend continuously between thefirst and second sections of the rigid film.

A neutral plane having a width substantially defined by the first widthmay be substantially symmetrical with respect to the folding axis whenthe foldable display device is folded or unfolded. The firstdouble-sided adhesive film at least in part may locate the neutral planewithin the flexible display module.

The lower flexible module may include an impact absorbing layer. Anentire of an upper surface of the first double-sided adhesive film maybe directly attached to the lower flexible module. A lower surface ofthe first double-sided adhesive film may be directly attached to thefirst and second sections of the rigid film.

The foldable display device assembly may further comprise a firsthousing coupled to the first section of the rigid film, a second housingcoupled to the second section of the rigid film, and a hinge connectedbetween the first and second housings to correspond to the folding axis.

The first double-sided adhesive film may comprise a third section and afourth section. The third and fourth sections may be separated from eachother by a second width that is relatively greater than the first width.The third and fourth sections of the first double-sided adhesive filmmay be disposed above the first and second sections of the rigid film,respectively. An inner side of the first section of the rigid film maybe relatively closer to the folding axis than an inner side of the thirdsection of the first double-sided adhesive film to the folding axis. Aninner side of the second section of the rigid film may be relativelycloser to the folding axis than an inner side of the fourth section ofthe first double-sided adhesive film to the folding axis.

A neutral plane having a width substantially defined by the second widthmay be substantially symmetrical with respect to the folding axis whenthe foldable display device is folded or unfolded. The neutral plane maybe located within the flexible display module.

The foldable display device may further comprise a height compensationfilm being disposed between the third and fourth sections of the firstdouble-sided adhesive film and having substantially the same height asthe first double-sided adhesive film.

The height compensation film may comprise a double-sided common adhesivefilm extending continuously over the first and second sections of therigid film.

A neutral plane having a width substantially defined by the first widthmay be substantially symmetrical with respect to the folding axis whenthe foldable display device is folded or unfolded. The heightcompensation film may, at least in part, locate the neutral plane withinthe flexible display module.

The height compensation film may comprise a common film extendingcontinuously over the first and second sections of the rigid film andmay have an adhesive top surface and a non-adhesive bottom surface.

A neutral plane having a width substantially defined by the second widthmay be substantially symmetrical with respect to the folding axis whenthe foldable display device is folded or unfolded. The heightcompensation film may, at least in part, locate the neutral plane withinthe flexible display module.

The bottom surface of the height compensation film may comprise aninorganic material.

The height compensation film may be a common film extending continuouslyover the first and second sections of the rigid film and may have anon-adhesive top surface and an adhesive bottom surface.

A neutral plane having a width substantially defined by the second widthmay be substantially symmetrical with respect to the folding axis whenthe foldable display device is folded or unfolded. The heightcompensation film may, at least in part, locate the neutral plane withinthe flexible display module.

The height compensation film may comprise a fifth section and a sixthsection separated from each other by a third width that is relativelygreater than the first width and relatively smaller than the secondwidth. The fifth and sixth sections of the height compensation film maybe disposed above the first and second sections of the rigid film,respectively. An inner side of the first section of the rigid film maybe relatively closer to the folding axis than an inner side of the fifthsection of the height compensation film to the folding axis. An innerside of the second section of the rigid film may be relatively closer tothe folding axis than an inner side of the sixth section of the heightcompensation film to the folding axis. The height compensation film maycomprise a double-sided adhesive film.

A neutral plane having a width substantially defined by the third widthmay be substantially symmetrical with respect to the folding axis whenthe foldable display device is folded or unfolded. The neutral plane maybe located within the flexible display module.

The height compensation film may further comprise a fifth section and asixth section separated from each other by a third width that isrelatively greater than the first width and relatively smaller than thesecond width. The fifth and sixth sections of the height compensationfilm may be disposed above the first and second sections of the rigidfilm, respectively. An inner side of the first section of the rigid filmmay be relatively closer to the folding axis than an inner side of thefifth section of the height compensation film to the folding axis. Aninner side of the second section of the rigid film may be relativelycloser to the folding axis than an inner side of the sixth section ofthe height compensation film to the folding axis. The heightcompensation film may have an adhesive top surface and a non-adhesivebottom surface.

A neutral plane having a width substantially defined by the second widthmay be substantially symmetrical with respect to the folding axis whenthe foldable display device is folded or unfolded. The heightcompensation film may, at least in part, locate the neutral plane withinthe flexible display module.

The bottom surface of the height compensation film may comprise aninorganic material.

The height compensation film may further comprise a fifth section and asixth section separated from each other by a third width that isrelatively greater than the first width and relatively smaller than thesecond width. The fifth and sixth sections of the height compensationfilm may be disposed above the first and second sections of the rigidfilm, respectively. An inner side of the first section of the rigid filmmay be relatively closer to the folding axis than an inner side of thefifth section of the height compensation film to the folding axis. Aninner side of the second section of the rigid film may be relativelycloser to the folding axis than an inner side of the sixth section ofthe height compensation film to the folding axis. The heightcompensation film may have a non-adhesive top surface and an adhesivebottom surface.

A neutral plane having a width substantially defined by the second widthmay be substantially symmetrical with respect to the folding axis whenthe foldable display device is folded or unfolded. The neutral plane maybe located within the flexible display module.

The lower flexible module may include an impact absorbing layer. Thefirst section of the rigid film and the second section of the rigid filmmay be separated from each other by the space such that a distancebetween an inner side surface of the first section and an inner sidesurface of the second section may be the first width. The first sectionof the rigid film may have an upper surface having a first portion and asecond portion. The first portion may be connected to the inner sidesurface of the first section. The second portion may be connected to thefirst portion. The second section of the rigid film may have an uppersurface having a third portion and a fourth portion. The third portionmay be connected to the inner side surface of the second section. Thefourth portion may be connected to the third portion. The firstdouble-sided adhesive film may not be fixed to the first and thirdportions. The first double-sided adhesive film may be fixed to thesecond and fourth portions.

The foldable display device assembly may further comprise a firsthousing coupled to the first section of the rigid film, a second housingcoupled to the second section of the rigid film, and a hinge connectedbetween the first and second housings to correspond to the folding axis.

According to an embodiment of the invention, a foldable display deviceassembly may comprise a rigid film, a first double-sided adhesive film,a lower flexible module, a second double-sided adhesive film, a flexibledisplay module, a third double-sided adhesive film, and an upperflexible. The rigid film may comprise first and second sections. Therigid film may be foldable about a folding axis disposed between thefirst and second sections. The first double-sided adhesive film may bedisposed on the rigid film. The lower flexible module may be disposed onthe first double-sided adhesive film. The second double-sided adhesivefilm may be disposed on the lower flexible module. The flexible displaymodule may be disposed on the second double-sided adhesive film. Theflexible display module may have an electroluminescent unit. The thirddouble-sided adhesive film may be disposed on the flexible displaymodule. The upper flexible module may be disposed on the thirddouble-sided adhesive film. The first and second sections may have asubstantially constant thickness. The rigid film may further comprise asubstantially reduced thickness section located between the first andsecond sections.

The substantially reduced thickness section may have a thicknesssubstantially varied along a predetermined direction.

According to the aforementioned and other embodiments of the invention,since a rigid film is disposed below a low flexible module, non-foldingregions can be maintained to be substantially flat. Accordingly, thedeformation of a flexible display module and the degradation of displayquality can be reduced or prevented.

In addition, since a single-sided adhesive film is disposed between theflexible display module and the rigid film, the deformation of theflexible display module during the fabrication or use of a foldabledisplay device can be minimized.

According to an embodiment of the invention, a foldable display deviceassembly includes: a rigid film having first and second sections spacedapart from each other, the rigid film being foldable about a foldingaxis disposed between the first and second sections of the rigid film;an adhesion structure having first and second adhesion sections spacedapart from each other, the first and second adhesion sections beingdisposed on the first and second sections of the rigid film,respectively; a lower flexible module disposed on the adhesionstructure; a flexible display module disposed on the lower flexiblemodule; and an upper flexible module disposed on the flexible displaymodule. At least a portion of a lower surface of the first adhesionsection corresponds to a first lower adhesion region to which an uppersurface of the first section of the rigid film is adhered, at least aportion of an upper surface of the first adhesion section corresponds toa first upper adhesion region to which a lower surface of the lowerflexible module is adhered, and an area of the first lower adhesionregion is substantially different from an area of the first upperadhesion region. At least a portion of a lower surface of the secondadhesion section corresponds to a second lower adhesion region to whichan upper surface of the second section of the rigid film is adhered, atleast a portion of an upper surface of the second adhesion sectioncorresponds to a second upper adhesion region to which a lower surfaceof the lower flexible module is adhered, and an area of the second loweradhesion region is substantially different from an area of the secondupper adhesion region.

The lower flexible module may continuously extend over the first andsecond sections of the rigid film.

A distance between the first and second lower adhesion regions may besubstantially greater than a distance between the first and secondsections of the rigid film.

The entire upper surface of the first adhesion section and the entireupper surface of the second adhesion section may be adhered to the lowersurface of the lower flexible module.

The distance between the first and second lower adhesion regions may besubstantially greater than a distance between the first and second upperadhesion regions.

A distance between the first and second upper adhesion regions may besubstantially greater than a distance between the first and secondsections of the rigid film.

The entire lower surface of the first adhesion section and the entirelower surface of the second adhesion section may be adhered to the uppersurface of the first section of the rigid film and the upper surface ofthe second section of the rigid film, respectively.

A distance between the first and second lower adhesion regions may besubstantially greater than a distance between the first and secondsections of the rigid film.

The lower flexible module may have a substantially lower lighttransmittance than the upper flexible module.

According to an embodiment of the invention, a foldable display deviceassembly includes: a plate having a first section, a second section, anda connection section connected between the first and second sections,the plate being foldable about a folding axis disposed between the firstand second sections, the first and second sections being rigid orsemi-rigid, the connection section having a foldability and a firstwidth measured in a direction from the first section of the plate to thesecond section of the plate when the foldable display device assembly isunfolded; a lower flexible module disposed on the plate; a firstdouble-sided adhesive film disposed on the lower flexible module; aflexible display module disposed on the first double-sided adhesivefilm, the flexible display module having an electroluminescent unit; asecond double-sided adhesive film disposed on the flexible displaymodule; and an upper flexible module disposed on the second double-sidedadhesive film. The connection section of the plate has an averagethickness substantially smaller than the first and second sections ofthe plate, and the lower flexible module has a substantially lower lighttransmittance than the upper flexible module.

The foldable display device may further include a third double-sidedadhesive film disposed between the plate and the lower flexible module.The third double-sided adhesive film may extend continuously over thefirst and second sections of the plate.

A neutral plane having a width substantially smaller than the firstwidth may be substantially symmetrical with respect to the folding axiswhen the foldable display device assembly is folded or unfolded, and thethird double-sided adhesive film may at least in part locate the neutralplane within a foldable region of the flexible display module.

The connection section of the plate may have a portion having an averagethickness decreasing in the direction in which the first width ismeasured.

The connection section of the plate may have a downwardly openingrecess.

The downwardly opening recess may have at least one of a rounded innercorner and/or a rounded outer corner.

The connection section of the plate may have an upwardly opening recess.

The upwardly opening recess may have a rounded inner corner.

The connection section of the plate may have an upwardly opening recess.

The upwardly opening recess may have a rounded inner corner.

The connection section of the plate may have a plurality of holes.

The foldable display device assembly may further include a thirddouble-sided adhesive film disposed between the plate and the lowerflexible module. The third double-sided adhesive film may include thirdand fourth sections separated from each other, the third section of thethird double-sided adhesive film may be disposed between the firstsection of the plate and the lower flexible module, and the fourthsection of the third double-sided adhesive film may be disposed betweenthe second section of the plate and the lower flexible module.

The foldable display device assembly may further include: a buffer filmdisposed on the plate; and a third double-sided adhesive film disposedbetween the buffer film and the lower flexible module. The buffer filmmay prevent an adhesion between the third double-sided adhesive film andthe plate from decreasing due to a difference in a physical propertybetween the plate and the third double-sided adhesive film.

The buffer film may include a non-metallic inorganic material.

The non-metallic inorganic material may include silicon.

The plate may include a metal, and the third double-sided adhesive filmmay include an organic material.

According to an embodiment of the invention, a foldable display deviceassembly includes: a rigid film having first and second sections betweenwhich a space having a width measured in a direction from the firstsection of the rigid film to the second section of the rigid film whenthe foldable display device assembly is unfolded is disposed, the rigidfilm being foldable about a folding axis disposed between the first andsecond sections; a buffer film disposed on the rigid film; a firstdouble-sided adhesive film disposed on the buffer film; a lower flexiblemodule disposed on the first double-sided adhesive film; a seconddouble-sided adhesive film disposed on the lower flexible module; aflexible display module disposed on the second double-sided adhesivefilm, the flexible display module having an electroluminescent unit; athird double-sided adhesive film disposed on the flexible displaymodule; and an upper flexible module disposed on the third double-sidedadhesive film. The lower flexible module has a substantially lower lighttransmittance than the upper flexible module, and the buffer filmprevents an adhesion between the rigid film and the first double-sidedadhesive film from decreasing due to a difference in a physical propertybetween the rigid film and the first double-sided adhesive film.

The buffer film may include a non-metallic inorganic material.

The non-metallic inorganic material may include silicon.

The plate may include a metal, and the first double-sided adhesive filmmay include an organic material.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention, andtogether with the description serve to explain the inventive concepts.

FIG. 1 is a perspective view of a foldable terminal equipped with afoldable display device according to an embodiment of the invention;

FIG. 2 is a cross-sectional view, taken along line II-II′ of FIG. 1, ofthe foldable display device of FIG. 1;

FIG. 3 is a plan view of the foldable display device of FIG. 1;

FIGS. 4, 5, 6, and 7 are cross-sectional views of foldable displaydevices according to other embodiments of the invention;

FIG. 8 is a cross-sectional view of a foldable display device accordingto another embodiment of the invention;

FIGS. 9, 10, and 11 are cross-sectional views of foldable displaydevices according to other embodiments of the invention;

FIG. 12 is a cross-sectional view of a foldable display device accordingto yet another embodiment of the invention; and

FIGS. 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, and 23 are cross-sectionalviews of foldable display devices according to other embodiments of theinvention.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of various embodiments or implementations of theinvention. As used herein “embodiments” and “implementations” areinterchangeable words that are non-limiting examples of devices ormethods employing one or more of the inventive concepts disclosedherein. It is apparent, however, that various embodiments may bepracticed without these specific details or with one or more equivalentarrangements. In other instances, well-known structures and devices areshown in block diagram form in order to avoid unnecessarily obscuringvarious embodiments. Further, various embodiments may be different, butdo not have to be exclusive. For example, specific shapes,configurations, and characteristics of an embodiment may be used orimplemented in another embodiment without departing from the inventiveconcepts.

Unless otherwise specified, the illustrated embodiments are to beunderstood as providing features of varying detail of some ways in whichthe inventive concepts may be implemented in practice. Therefore, unlessotherwise specified, the features, components, modules, layers, films,panels, regions, and/or aspects, etc. (hereinafter individually orcollectively referred to as “elements”), of the various embodiments maybe otherwise combined, separated, interchanged, and/or rearrangedwithout departing from the inventive concepts.

The use of cross-hatching and/or shading in the accompanying drawings isgenerally provided to clarify boundaries between adjacent elements. Assuch, neither the presence nor the absence of cross-hatching or shadingconveys or indicates any preference or requirement for particularmaterials, material properties, dimensions, proportions, commonalitiesbetween illustrated elements, and/or any other characteristic,attribute, property, etc., of the elements, unless specified. Further,in the accompanying drawings, the size and relative sizes of elementsmay be exaggerated for clarity and/or descriptive purposes. When anembodiment may be implemented differently, a specific process order maybe performed differently from the described order. For example, twoconsecutively described processes may be performed substantially at thesame time or performed in an order opposite to the described order.Also, like reference numerals denote like elements.

When an element, such as a layer, is referred to as being “on,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, connected to, or coupled to the other element or layer orintervening elements or layers may be present. When, however, an elementor layer is referred to as being “directly on,” “directly connected to,”or “directly coupled to” another element or layer, there are nointervening elements or layers present. To this end, the term“connected” may refer to physical, electrical, and/or fluid connection,with or without intervening elements. Further, the D1-axis, the D2-axis,and the D3-axis are not limited to three axes of a rectangularcoordinate system, such as the x, y, and z—axes, and may be interpretedin a broader sense. For example, the D1-axis, the D2-axis, and theD3-axis may be perpendicular to one another, or may represent differentdirections that are not perpendicular to one another. For the purposesof this disclosure, “at least one of X, Y, and Z,” “at least oneselected from the group of X, Y, and Z,” and “at least one selected fromthe group consisting of X, Y, and Z” may be construed as X only, Y only,Z only, or any combination of two or more of X, Y, and Z, such as, forinstance, XYZ, XYY, YZ, and ZZ. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items.

Although the terms “first,” “second,” etc. may be used herein todescribe various types of elements, these elements should not be limitedby these terms. These terms are used to distinguish one element fromanother element. Thus, a first element discussed below could be termed asecond element without departing from the teachings of the disclosure.

Spatially relative terms, such as “beneath,” “below,” “under,” “lower,”“above,” “upper,” “over,” “higher,” “side” (e.g., as in “sidewall”), andthe like, may be used herein for descriptive purposes, and, thereby, todescribe one elements relationship to another element(s) as illustratedin the drawings. Spatially relative terms are intended to encompassdifferent orientations of an apparatus in use, operation, and/ormanufacture in addition to the orientation depicted in the drawings. Forexample, if the apparatus in the drawings is turned over, elementsdescribed as “below” or “beneath” other elements or features would thenbe oriented “above” the other elements or features. Thus, the exemplaryterm “below” can encompass both an orientation of above and below.Furthermore, the apparatus may be otherwise oriented (e.g., rotated 90degrees or at other orientations), and, as such, the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting. As used herein, thesingular forms, “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. Moreover,the terms “comprises,” “comprising,” “includes,” and/or “including,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, components, and/orgroups thereof, but do not preclude the presence or addition of one ormore other features, integers, steps, operations, elements, components,and/or groups thereof. It is also noted that, as used herein, the terms“substantially,” “about,” and other similar terms, are used as terms ofapproximation and not as terms of degree, and, as such, are utilized toaccount for inherent deviations in measured, calculated, and/or providedvalues that would be recognized by one of ordinary skill in the art.

Various embodiments are described herein with reference to sectionaland/or exploded illustrations that are schematic illustrations ofidealized embodiments and/or intermediate structures. As such,variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, embodiments disclosed herein should not necessarily beconstrued as limited to the particular illustrated shapes of regions,but are to include deviations in shapes that result from, for instance,manufacturing. In this manner, regions illustrated in the drawings maybe schematic in nature and the shapes of these regions may not reflectactual shapes of regions of a device and, as such, are not necessarilyintended to be limiting.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure is a part. Terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and should not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.

FIG. 1 is a perspective view of a foldable terminal equipped with afoldable display device according to an embodiment of the invention.FIG. 2 is a cross-sectional view, taken along line II-II′ of FIG. 1, ofthe foldable display device of FIG. 1. FIG. 3 is a plan view of thefoldable display device of FIG. 1.

As used herein, the term “foldable” encompasses partially foldable,foldable as a whole, rollable inwardly and/or outwardly and flexible,the term “module” refers to a structure including at least one film, andthe term “display device” not only encompasses any type of informationdisplay device such as a television (TV), a terminal, mobile phone,personal digital assistant or the like, but also encompasses an opticaldevice such as a light.

Referring to FIGS. 1 through 3, a foldable display device 100 may beformed as a substantial rectangle in a plan view. The foldable displaydevice 100 may be formed as a substantial rectangle with right-angledcorners or with rounded corners in a plan view. The foldable displaydevice 100 may include four sides or edges. The foldable display device100 may include long sides LS1 and LS2 and short sides SS1 and SS2.

Unless specified otherwise, the terms “top” and “above”, as used herein,may refer to a display surface's side when a display module is in itsunfolded state, and the terms “bottom” and “below”, as used herein, mayrefer to the opposite side to the display surface's side when thedisplay module is in its unfolded state. Also, in a plan view, the terms“on” or “above”, “below” or “beneath”, “left”, and “right”, as usedherein, refer to directions when the display surface is viewed fromabove.

In a plan view, in the foldable display device 100, which issubstantially rectangular in shape, or a display module 210 included inthe foldable display device 100, the long side on the left willhereinafter be referred to as a first long side LS1, the long side onthe right will hereinafter be referred to as a second long side LS2, theshort side at the top will hereinafter be referred to as a first shortside SS1, and the short side at the bottom will hereinafter be referredto as a second short side SS2. The length of the first and second longsides LS1 and LS2 of the foldable display device 100 may be about 1.2 toabout 2.5 times the length of the first and second short sides SS1 andSS2 of the foldable display device 100, but the invention is not limitedthereto.

The foldable display device 100 may be bent in a folding direction FDalong a folding axis AXIS_F, which extends across the first and secondshort sides SS1 and SS2. That is, the foldable display device 100 may beswitched between a folded (compact) state, which is a state in which thefoldable display device 100 is folded in the folding direction FD alongthe folding axis AXIS_F, and an unfolded (expanded) state. Grooves (ornotches) G, which are recessed toward the center of gravity in a planview, may be formed at the first and second short sides SS1 and SS2 thatmeet the folding axis AXIS_F, and hinge members may be coupled to thegrooves G. However, the invention is not limited to this. The switchingof the foldable display device 100 between the folded state and theunfolded state will be described later after describing the elements ofthe foldable display device 100.

The foldable display device 100 may include the display module 210,which is also referred to as a flexible display module, a display panel,or a flexible display panel, an upper flexible module 220, a lowerflexible module 230, and a rigid film 240. The foldable display device100 may further include double-sided adhesive films (NAD1, NAD2, and250) disposed (or interposed) between the display module 210, the upperflexible module 220, the lower flexible module 230, and the rigid film240.

Examples of the double-sided adhesive films (NAD1, NAD2, and 250)include optical clear adhesives (OCAs), pressure sensitive adhesives(PSAs), and the like.

The display module 210 may display an image based on an input datasignal. An organic light-emitting diode (OLED) display module, a liquidcrystal display (LCD) module, a plasma display panel (PDP) module, anelectrophoretic display (EPD) module, an electro-wetting display module,a quantum dot light-emitting display (QLED) module, a microlight-emitting diode (micro-LED) module or other type of display may beused as the display module 210. In the embodiment of FIGS. 1 through 3,an OLED display module is used as the display module 210 for ease ofdescription.

The display module 210 may include a flexible substrate comprising aflexible polymer material such as polyimide. Accordingly, the displaymodule 210 can be bent, folded, or rolled.

The display module 210 may generally have a substantially similar shapeto the foldable display device 100 in a plan view, but the invention isnot limited thereto. That is, alternatively, at least one side (e.g.,the first long side LS1) of the display module 210 may be bent into asubstantially curved shape, or may be bent in a vertical direction. Acircuit board including wires transmitting signals necessary for drivingthe display module 210 may be connected via at least one side of thedisplay module 210. The circuit board may be disposed to overlap withthe display module 210 in a thickness direction.

The display module 210 may include a display area DPA, which displays animage, and a non-display area NDA, which does not display an image.

The display area DPA may be disposed at the center of the display module210. The display area DPA may include pixels (or electroluminescentunits). The pixels may include a light-emitting layer and a circuitlayer controlling the amount of light emitted by the light-emittinglayer. The circuit layer may include display wires, display electrodes,and at least one transistor. The light-emitting layer may comprise anorganic light-emitting material. The light-emitting layer may be sealedby an encapsulation film. The encapsulation film seals thelight-emitting layer and can thus prevent the penetration of externalmoisture or the like. The encapsulation film may include a single ormultilayer inorganic film or a stack of at least one inorganic film andat least one organic film.

The display area DPA, like the foldable display device 100, may be in agenerally rectangular shape with right-angled corners or with roundedcorners, but the invention is not limited thereto. That is,alternatively, the display area DPA may be in various shapes other thana substantially rectangular shape, such as a substantially polygonalshape (e.g., a substantially square shape), a substantially circularshape, or a substantially elliptical shape.

The non-display area NDA may be disposed in the periphery of the displayarea DPA. The entire display module 210 except for the display area DPAmay account for the non-display area NDA. The non-display area NDA mayrange from the outer boundaries of the display area DPA to the edges ofthe display module 210. In the non-display area NDA, signal wires ordriving circuits for applying signals to the display area DPA may bedisposed. Also, in the non-display area NDA, an outermost black matrixmay be disposed.

The display module 210 may include a folding region FR (or a bendableregion). The folding region FR will be described later together with therigid film 240.

The upper flexible module 220 may be disposed above the display module210 to overlap with the display module 210 in the thickness direction.The upper flexible module 220 and the lower flexible module 230 may beused to control the vertical position of a neutral plane NP of thefoldable display device 100. When the foldable display device 100 isbent or folded, tensile stress may be generated on one side of thefoldable display device 100, compressive stress may be generated on theopposite side of the foldable display device 100, and in the middle,there exists a plane where no stress exists. The plane wheresubstantially no stress exists is defined as the neutral plane NP.Bending stress is not generated on the neutral plane NP. For example,the upper flexible module 220 (or an upper neutral plane controllerUNPC) and the lower flexible module 230 (or a lower neutral planecontroller LNPC) substantially position the neutral plane NP of thefoldable display device 100 in the display module 210 (or in a layer ofthe display module 210 where driving transistors are formed).

The upper flexible module 220 may include one or more optical films anda window. The optical films may include a polarizing film, a micro-lens,a prism film, and the like. The optical films may have substantially thesame shape as the display module 210 (or the display area DPA of thedisplay module 210). The optical films may not be provided.

The window may be disposed above the optical films. The window coversand protects the display module 210. The window may be formed by using atransparent material. The window may comprise plastic, in which case,the window may have flexibility.

Examples of plastic that may be applicable to the window include, butare not limited to, polyimide, polyacrylate, polymethyl methacrylate(PMMA), polycarbonate (PC), polyethylene naphthalate (PEN),polyvinylidene chloride (PVDC), polyvinylidene difluoride (PVDF),polystyrene, an ethylene vinyl alcohol copolymer, polyethersulphone(PES), polyetherimide (PEI), polyphenylene sulfide (PPS), polyallylate,tri-acetyl cellulose (TAC), and cellulose acetate propionate (CAP), andthe window may comprise at least one of these plastic materials.

An upper double-sided adhesive film NAD1 may be disposed between theupper flexible module 220 and the display module 210, and the upperflexible module 220 may be attached (or coupled) to the top surface ofthe display module 210 via the upper double-sided adhesive film NAD1.The upper double-sided adhesive film NAD1, which is a film havingadhesiveness on both the top and bottom surfaces thereof, may be, forexample, an optically clear adhesive (OCA).

The lower flexible module 230 may overlap with the display module 210 inthe thickness direction and may be disposed below the display module210.

The lower flexible module 230 may include one or more functional layers.The functional layer may be layers performing a heat dissipationfunction, an electromagnetic shielding function, a grounding function, abuffering function, a strength enhancement function, a support function,a bonding function, a pressure sensing function, and a digitizingfunction. The functional layers may be, for example, a supportingsubstrate, a heat dissipation layer, an electromagnetic wave shieldinglayer, an impact absorbing layer, a bonding layer, a pressure sensor, adigitizer, and the like.

The lower flexible module 230 may have relatively lower lighttransmittance than the upper flexible module 220. That is, the upperflexible module 220 may have a relatively high light transmittance andmay transmit light (or an image) emitted from the display area DPA ofthe display module 210 upwardly, and the lower flexible module 230 mayhave a relatively low light transmittance and may block light which maybe emitted downwardly from the display area DPA of the display module210 and, then, may be reflected by the rigid film 240.

A lower double-sided adhesive film NAD2 may be disposed between thelower flexible module 230 and the display module 210, and the lowerflexible module 230 may be attached (or coupled) to the bottom surfaceof the display module 210 via the lower double-sided adhesive film NAD2.The lower double-sided adhesive film NAD2, which is a film havingadhesiveness on both the top and bottom surfaces thereof, like the upperdouble-sided adhesive film NAD1, may be, for example, a pressuresensitive adhesive (PSA).

The lower flexible module 230 may include an impact absorbing layer. Theimpact absorbing layer can prevent impact applied thereto from theoutside (for example, from below the display module 210) from beingtransmitted to the display module 210. For example, the impact absorbinglayer may comprise polyurethane (PU), thermoplastic polyurethane (TPU),silicon (Si), or polydimethyl acrylamide (PDMA).

The rigid film 240 may overlap with the lower flexible module 230 in thethickness direction and may be disposed below the lower flexible module230.

The rigid film 240 may comprise a metal material such as steel specialuse stainless (SUS) or aluminum (Al) or a polymer such as PMAA, PC,polyvinyl alcohol (PVA), acrylonitrile-butadiene-styrene (ABS), orpolyethylene terephthalate (PET). The rigid film 240 can prevent thebending of the display module 210 by an external force or can alleviatethe degree to which the display module 210 is bent by an external force(e.g., the angle or the curvature radius to which the display module 210is bent by an external force). That is, the rigid film 240 can maintainthe display module 210 in a relatively flat configuration even when anexternal force is applied. The rigid film 240 may be rigid orsemi-rigid. For example, the rigid film 240 may be a SUS film having athickness of about 150 μm to about 200 μm. In another example, the rigidfilm 240 may be an Al film having a thickness of about 150 μm to about200 μm.

Referring to FIG. 5, a double-sided adhesive film 250 may be disposedbetween the rigid film 240 and the lower flexible module 230, and therigid film 240 may be attached to the lower flexible module 230 via thedouble-sided adhesive film 250.

Protrusions or grooves (or holes) may be formed at the bottom of therigid film 240, and a housing included in the foldable terminal may becoupled to the rigid film 240 (or the foldable display device 100) viathe protrusions or the grooves.

The rigid film 240 may include first and second plates (or first andsecond sections) 241 and 242, which are separate from each other in aleft-to-right direction (or a horizontal direction). Referring to FIG.6, the first and second plates 241 and 242 may be disposed onsubstantially the same plane and may be a reference distance D0 apartfrom each other in the left-to-right direction. For example, thereference distance D0 may be about 0.1 mm or less. The first and secondplates 241 and 242 may be substantially symmetrical with respect to afolding line FL (i.e., a line that extends in the thickness direction tomeet the folding axis AXIS_F), but the invention is not limited thereto.For example, the first and second plates 241 and 242 may besubstantially asymmetrical with respect to the folding line FL.

The first and second plates 241 and 242 are illustrated in FIG. 2 asbeing separated from each other, but the invention is not limitedthereto. That is, the example of FIG. 2 is simply for showing that thefirst and second plates 241 and 242 are separate (or discrete) from eachother. In another example, the inner sides of the first and secondplates 241 and 242 may be at least partially in contact with each other.

In one embodiment, the first and second plates 241 and 242 may have sucha shape that their thickness decreases in a direction toward the foldingline FL. For example, the thickness of the first and second plates 241and 242 may decrease stepwise. In another example, the thickness of thefirst and second plates 241 and 242 may decrease continuously. In a casewhere the first and second plates 241 and 242 have such a shape thattheir thickness decreases in the direction toward the folding line FL,the flexibility of the first and second plates 241 and 242 may berelatively high near the folding line FL.

The double-sided adhesive film 250 may be disposed between the first andsecond plates 241 and 242 (or the rigid film 240) and the lower flexiblemodule 230, and the first and second plates 241 and 242 may be coupledto the bottom of the lower flexible module 230 via the double-sidedadhesive film 250.

The double-sided adhesive film 250 may include a first double-sidedadhesive film (or a third section) 251 and a second double-sidedadhesive film (or a fourth section) 252, which are separate from eachother.

In a first non-folding region NFR1, the first double-sided adhesive film251 may overlap with the display module 210 (or the lower flexiblemodule 230) in the thickness direction and may be disposed between thelower flexible module 230 and the first plate 241. In this case, thefirst plate 241 may be coupled to the lower flexible module 230 via thefirst double-sided adhesive film 251. Similarly, in a second non-foldingregion NFR2, the second double-sided adhesive film 252 may overlap withthe display module 210 (or the lower flexible module 230) in thethickness direction and may be disposed between the lower flexiblemodule 230 and the second plate 242. In this case, the second plate 242may be coupled to the lower flexible module 230 via the seconddouble-sided adhesive film 252.

The first and second double-sided adhesive film 251 and 252 may bedisposed on substantially the same plane and may be a first distance D1apart from each other in the left-to-right direction. The first distanceD1 may be relatively greater than the reference distance D0. The firstand second double-sided adhesive films 251 and 252 may be bilaterallysymmetrical with respect to the folding line FL.

The inner side of the first plate 241 may be relatively closer than theinner side of the second plate 242 to the folding line FL (or thefolding axis AXIS_F), and the inner side of the second plate 242 may berelatively closer than the inner side of the second double-sidedadhesive film 252 to the folding line FL.

In this case, the folding region FR and the first and second non-foldingregions NFR1 and NFR2 of the display module 210 (or the foldable displaydevice 100) may be substantially set or substantially defined by thefirst and second double-sided adhesive films 251 and 252. The first andsecond non-folding regions NFR1 and NFR2, which are regions where thefirst and second plates 241 and 242 are coupled to the lower flexiblemodule 230 via the first and second double-sided adhesive films 251 and252, may hardly be bent by an external force and may be generally flat.That is, the first and second non-folding regions NFR1 and NFR2 may bedefined as regions where the rigid film 240 (or the first and secondplates 241 and 242), the double-sided adhesive film 250 (or the firstand second double-sided adhesive films 251 and 252), and the displaymodule 210 overlap with one another and are coupled (or attached) to oneanother. The folding region FR may be a region that is not directlycoupled to (or supported by) the first and second plates 241 and 242 andmay be bent by an external force to a relatively greater extent than thefirst and second non-folding regions NFR1 and NFR2. For example, thedegree to which the folding region FR is deformed by an external force(or the angle to which the folding region FR is bent by an externalforce) may be about three or more times the degree to which the firstand second non-folding regions NFR1 and NFR2 are deformed by theexternal force (or the angle to which the first and second non-foldingregions NFR1 and NFR2 are bent by the external force). The foldingregion FR may be switched from a folded state to an unfolded state orvice versa by an external force.

As illustrated in FIG. 3, the folding region FR may have a generallyrectangular shape and may vertically extend from the first short sideSS1 to the second short side SS2 to have a first width W1 with respectto the folding axis AXIS_F, which extends vertically. The first width W1may be substantially the same as, or at least substantially similar tothe first distance D1 between the first and second double-sided adhesivefilms 251 and 252 as shown in FIG. 6.

The first non-folding region NFR1 may have a second width W2 and may beconnected to one side (e.g., the left side with respect to the foldingaxis AXIS_F) of the folding region FR. Similarly, the second non-foldingregion NFR2 may have a third width W3 and may be connected to the otherside (e.g., the right side with respect to the folding axis AXIS_F) ofthe folding region FR. The second width W2 of the first non-foldingregion NFR1 may be substantially the same as, or substantially differentfrom the third width W3 of the second non-folding region NFR2.

The foldable display device 100 may further include a single-sidedadhesive film (or a height compensation film) 260.

The single-sided adhesive film 260 may overlap with the folding regionFR of the display module 210 in the thickness direction and may bedisposed between the lower flexible module 230 and the rigid film 240.That is, the single-sided adhesive film 260 may be disposed onsubstantially the same plane as the first and second double-sidedadhesive films 251 and 252.

The single-sided adhesive film 260 may have substantially the samethickness as the double-sided adhesive film 250. The single-sidedadhesive film 260 may be a second distance apart from the firstdouble-sided adhesive film 251 and may be a third distance D3 apart fromthe second double-sided adhesive film 252. The third distance D3 may besubstantially the same as, or substantially different from the seconddistance D2. For example, the second and third distances D2 and D3 maybe about 0.1 mm or less or may be substantially zero.

The single-sided adhesive film 260 is a film having adhesiveness on atleast one of the top and bottom surfaces thereof. For example, thesingle-sided adhesive film 260 may have adhesiveness on the top surfacethereof, but no adhesiveness on the bottom surface thereof. That is,only the top surface of the single-sided adhesive film 260 may haveadhesiveness. In this example, the single-sided adhesive film 260 may beattached to the bottom of the lower flexible module 230, but not to therigid film 240 (or the first and second plates 241 and 242). In anotherexample, the top and bottom surfaces of the single-sided adhesive film260 may both have adhesiveness.

In a case where the single-sided adhesive film 260 has adhesiveness onthe top surface thereof, but no adhesiveness on the bottom surfacethereof, the position of the neutral plane NP may be substantiallydetermined by the positions of the first and second double-sidedadhesive films 251 and 252, and the width of the neutral plane NP may besubstantially determined by the distance between the first and seconddouble-sided adhesive films 251 and 252, i.e., the first distance D1.The width of the neutral plane NP may be substantially determined by thefirst distance D1, but is not necessarily the same as the first distanceD1. For example, as the distance between the top surface of the rigidfilm 240 and the top surface of the upper flexible module 220 increases,the width of the neutral plane NP may become relatively smaller than thefirst distance D1. In another example, as the first distance D1decreases, the width of the neutral plane NP may become relativelygreater than the first distance D1.

In a case where the single-sided adhesive film 260 has adhesiveness onboth the top and bottom surfaces thereof, the position of the neutralplane NP may be substantially determined by the positions of the firstand second plates 241 and 242, and the width of the neutral plane NP maybe substantially determined by the distance between the first and secondplates 241 and 242, i.e., the reference distance D0. The width of theneutral plane NP may be substantially determined by the referencedistance D0, but is not necessarily the same as the reference distanceD0. For example, as the distance between the top surface of the rigidfilm 240 and the top surface of the upper flexible module 220 increases,the width of the neutral plane NP may become relatively smaller than thereference distance D0. In another example, as the reference distance D0decreases, the width of the neutral plane NP may become relativelygreater than the reference distance D0.

The single-sided adhesive film 260 may have substantially the sameflexible characteristic as, or a substantially similar flexiblecharacteristic to, the lower flexible module 230 (or the impactabsorbing layer of the lower flexible module 230).

The rigid film 240 (or the first and second plates 241 and 242) maysupport the display module 210 (and the lower flexible module 230) viathe single-sided adhesive film 260. Accordingly, deformation of thedisplay module 210 during the fabrication and/or use of the foldabledisplay device 100 can be reduced or prevented. For example, the displaymodule 210 and the lower flexible module 230 can be prevented from beingdeformed in the folding region FR by a lamination roller during alamination process for attaching the rigid film 240 to the lowerflexible module 230.

As already mentioned above, since the rigid film 240 is disposed belowthe display module 210 (or the lower flexible module 230), thenon-folding regions NFR1 and NFR2 can be maintained to be substantiallyflat. In addition, since the single-sided adhesive film 260 is disposedbetween the display module 210 and the rigid film 240, the deformationof the display module 210 during the fabrication or use of the foldabledisplay device 100 can be reduced or prevented. As a result, thedegradation of display quality can be reduced or prevented.

FIG. 2 illustrates the single-sided adhesive film 260 as havingsubstantially the same thickness as each of the first and seconddouble-sided adhesive films 251 and 252, but the invention is notlimited thereto. For example, the thickness of the single-sided adhesivefilm 260 may be relatively smaller than the thickness of each of thefirst and second double-sided adhesive films 251 and 252. In anotherexample, in a case where the single-sided adhesive film 260 includessubstantially uneven patterns on the bottom surface thereof, the averagethickness of the single-sided adhesive film 260 may be relativelysmaller than the thickness of each of the first and second double-sidedadhesive films 251 and 252.

FIGS. 4 through 7 are cross-sectional views of foldable display devicesaccording to other embodiments of the invention.

Referring to FIG. 4, a foldable display device 100_1 substantiallydiffers from the foldable display device 100 of FIG. 2 in that itfurther includes first and second buffer films 471 and 472.

First and second double-sided adhesive films 451 and 452 may besubstantially the same as the first and second double-sided adhesivefilms 251 and 252 of FIG. 2, and thus, detailed descriptions thereofwill be omitted.

The first buffer film 471 may be disposed between the first double-sidedadhesive film 451 and a first plate 241 in a thickness direction, andthe second buffer film 472 may be disposed between the seconddouble-sided adhesive film 452 and a second plate 242. The first bufferfilm 471 may have adhesiveness on the bottom surface thereof and may beattached to the first plate 241, and the second buffer film 472 may haveadhesiveness on the bottom surface thereof and may be attached to thesecond plate 242.

The sum of the thicknesses of the first double-sided adhesive film 451and the first buffer film 471 may be substantially the same as thethickness of a single-sided adhesive film 260. Similarly, the sum of thethicknesses of the second double-sided adhesive film 452 and the secondbuffer film 472 may be substantially the same as the thickness of thesingle-sided adhesive film 260.

The first and second buffer films 471 and 472 may comprise anon-metallic inorganic material such as silicon (Si) (or amorphoussilicon). The first and second double-sided adhesive films 451 and 452may comprise an organic material, and the first and second plates 241and 242 may comprise a metal. In this case, the adhesion between thefirst and second double-sided adhesive films 451 and 452 and the firstand second plates 241 and 242 can be prevented from decreasing due tothe difference in a physical property such as a thermal expansioncoefficient between the metal from the first and second plates 241 and242 and the organic material from the first and second double-sidedadhesive films 451 and 452.

Referring to FIG. 5, a foldable display device 100_2 substantiallydiffers from the foldable display device 100 of FIG. 2 in that itincludes a first film (or a first height compensation film) 561 and asecond film (or a second height compensation film) 562.

In a folding region FR, the first film 561 may be disposed between alower flexible module 230 and a rigid film 240, and the second film 562may be disposed between the first film 561 and the rigid film 240. Thefirst film 561 may be attached to the bottom of the lower flexiblemodule 230, and the second film 562 may be attached to the bottom of thefirst film 561.

The sum of the thicknesses of the first and second films 561 and 562 maybe substantially the same as the thickness of a double-sided adhesivefilm 250.

The first film 561 may have adhesiveness on the top surface thereof. Atleast one of the bottom surface of the first film 561 and the topsurface of the second film 562 may have adhesiveness. The bottom surfaceof the second film 562 may not have adhesiveness. For example, the firstfilm 561 may be a double-sided adhesive film or a single-sided adhesivefilm having adhesiveness on the top surface thereof.

The second film 562 may be an inorganic film comprising an inorganicmaterial such as a metal. The adhesion of the second film 562 to thefirst and second plates 241 and 242 can be reduced when the second film562 comprises a metal than when the second film 562 comprises an organicmaterial.

The foldable display device 100_2 is illustrated in FIG. 5 as includingfirst and second double-sided adhesive films 251 and 252, but theinvention is not limited thereto. That is, alternatively, the foldabledisplay device 100_2 may include the first and second double-sidedadhesive films 451 and 452 and the first and second buffer films 471 and472 of FIG. 4. In this case, the sum of the thicknesses of the firstdouble-sided adhesive film 451 and the first buffer film 471 or the sumof the thicknesses of the second double-sided adhesive film 452 and thesecond buffer film 472 may be substantially the same as the sum of thethicknesses of the first and second films 561 and 562.

Referring to FIG. 6, a foldable display device 100_3 substantiallydiffers from the foldable display device 100 of FIG. 2 in that itincludes a first single-sided adhesive film (or a first heightcompensation film) 661 and a second single-sided adhesive film (or asecond height compensation film) 662.

The first and second single-sided adhesive films 661 and 662 may overlapwith each other in a folding region FR and may be disposed onsubstantially the same plane as first and second double-sided adhesivefilms 251 and 252.

The first single-sided adhesive film 661 may be disposed between a lowerflexible module 230 and a first plate 241. Similarly, the secondsingle-sided adhesive film 662 may be disposed between the lowerflexible module 230 and a second plate 242. The first and secondsingle-sided adhesive films 661 and 662 may be a fourth distance D4apart from each other in a left-to-right direction. The fourth distanceD4 may be substantially the same as, or relatively smaller than, areference distance D0. For example, the inner side of the firstsingle-sided adhesive film 661 (e.g., a side of the first single-sidedadhesive film 661 adjacent to a folding line FL) may be disposed onsubstantially the same plane as the inner side of the first plate 241.In another example, the inner side of the first plate 241 may berelatively closer than the inner side of the first single-sided adhesivefilm 661 to the folding line FL.

The first single-sided adhesive film 661 may be a second distance D2apart from the first double-sided adhesive film 251, and the secondsingle-sided adhesive film 662 may be a third distance D3 apart from thesecond double-sided adhesive film 252. The second and third distances D2and D3 may be substantially the same or may be substantially different.For example, the second and third distances D2 and D3 may be about 1 mmor less or may be substantially zero.

The first single-sided adhesive film 661 may have adhesiveness on thebottom surface thereof, but no adhesiveness on the top surface thereof.Similarly, the second single-sided adhesive film 662 may haveadhesiveness on the bottom surface thereof, but no adhesiveness on thetop surface thereof. In this case, the first single-sided adhesive film661 may be attached to the top surface of the first plate 241, and thesecond single-sided adhesive film 662 may be attached to the top surfaceof the second plate 242.

Each of the first and second single-sided adhesive films 661 and 662 isa film having adhesiveness on at least one of the top and bottomsurfaces thereof. For example, the first and second single-sidedadhesive films 661 and 662 may have adhesiveness on the top surfacesthereof, but no adhesiveness on the bottom surfaces thereof. That is,the first and second single-sided adhesive films 661 and 662 may beadhesive films that have adhesiveness only on the bottom surfacesthereof. In this case, the first and second single-sided adhesive films661 and 662 may be attached to the bottom of the lower flexible module230, but not to the first and second plates 241 and 242.

In a case where the first and second single-sided adhesive films 661 and662 have adhesiveness on the top surfaces thereof, but no adhesivenesson the bottom surface thereof, the position of a neutral plane NP may besubstantially determined by the positions of the first and seconddouble-sided adhesive films 251 and 252, and the width of the neutralplane NP may be substantially determined by the distance between thefirst and second double-sided adhesive films 251 and 252, i.e., a firstdistance D 1. The width of the neutral plane NP may be substantiallydetermined by the first distance D1, but is not necessarily the same asthe first distance D1. For example, as the distance between the topsurfaces of the first and second plates 241 and 242 and the top surfaceof an upper flexible module 220 increases, the width of the neutralplane NP may become relatively smaller than the first distance D1. Inanother example, as the first distance D1 decreases, the width of theneutral plane NP may become relatively greater than the first distanceD1.

In a case where the first and second single-sided adhesive films 661 and662 have adhesiveness on both the top surfaces and the bottom surfacesthereof, the position of the neutral plane NP may be substantiallydetermined by the positions of the first and second single-sidedadhesive films 661 and 662, and the width of the neutral plane NP may besubstantially determined by the distance between the first and secondsingle-sided adhesive films 661 and 662, i.e., the fourth distance D4.The width of the neutral plane NP may be substantially determined by thefourth distance D4, but is not necessarily the same as the fourthdistance D4. For example, as the distance between the top surface of thefirst and second single-sided adhesive films 661 and 662 and the topsurface of the upper flexible module 220 increases, the width of theneutral plane NP may become relatively smaller than the fourth distanceD4. In another example, as the fourth distance D4 decreases, the widthof the neutral plane NP may become relatively greater than the fourthdistance D4.

The foldable display device 100_3 is illustrated in FIG. 6 as includingthe first and second double-sided adhesive films 251 and 252, but theinvention is not limited thereto. That is, alternatively, the foldabledisplay device 100_3 may include the first and second double-sidedadhesive films 451 and 452 and the first and second buffer films 471 and472 of FIG. 4. In this case, the sum of the thicknesses of the firstdouble-sided adhesive film 451 and the first buffer film 471 or the sumof the thicknesses of the second double-sided adhesive film 452 and thesecond buffer film 472 may be substantially the same as the thickness ofeach of the first and second single-sided adhesive films 661 and 662.

Referring to FIG. 7, a foldable display device 100_4 substantiallydiffers from the foldable display device 100_3 of FIG. 6 (and thefoldable display device 100_2 of FIG. 5) in that it includes firstthrough fourth films (or first through fourth height compensation films)761 through 764.

The first and third films 761 and 763 may be substantially the same asthe first film 561 of FIG. 5 except for their locations. Similarly, thesecond and fourth films 762 and 764 may be substantially the same as thesecond film 562 of FIG. 5 except for their locations. Thus, detaileddescriptions of the first through fourth films 761 and 764 will beomitted.

The foldable display device 100_4 is illustrated in FIG. 7 as includingfirst and second double-sided adhesive films 251 and 252, but theinvention is not limited thereto. That is, alternatively, the foldabledisplay device 100_4 may include the first and second double-sidedadhesive films 451 and 452 and the first and second buffer films 471 and472 of FIG. 4. In this case, the sum of the thicknesses of the firstdouble-sided adhesive film 451 and the first buffer film 471 or the sumof the thicknesses of the second double-sided adhesive film 452 and thesecond buffer film 472 may be substantially the same as the sum of thethicknesses of the first and second films 761 and 762 (or the sum of thethicknesses of the third and fourth films 763 and 764).

FIG. 8 is a cross-sectional view of a foldable display device accordingto another embodiment of the invention.

Referring to FIG. 8, a foldable display device 100_5 substantiallydiffers from the foldable display device 100 of FIG. 2 in that itincludes a plate 840 and a double-sided adhesive film 850.

The plate 840 and the double-sided adhesive film 850 may besubstantially the same as, or substantially similar to, the rigid film240 and the double-sided adhesive film 250, respectively, of FIG. 2, andthus, detailed descriptions thereof will be omitted.

The plate 840 may be disposed below a lower flexible module 230, and thedouble-sided adhesive film 850 may be interposed between the lowerflexible module 230 and the plate 840. The plate 840 may be attached tothe lower flexible module 230 via the double-sided adhesive film 850.

The average height (or average thickness) of the plate 840 in a foldingregion FR may be relatively smaller than the average height (or averagethickness) of the plate 840 in a non-folding region. Similarly, thevolume (or area) of the plate 840 in the folding region FR may berelatively smaller than the volume (or area) of the plate 840 in thenon-folding region.

In the folding region FR, the plate 840 may include grooves (orrecesses) formed on the bottom surface thereof. The grooves may bearranged in series in a left-to-right direction.

A folding line FL may pass through one of the grooves or between a pairof adjacent grooves.

First corners (or outer corners) C1 and second corners (or innercorners) C2 of each of the grooves of the plate 840 may be rounded, butthe invention is not limited thereto.

Sidewalls S of each of the grooves (i.e., sidewalls between the firstcorners C1 and the second corners C2) may be sloped.

The density of the grooves or the width of the grooves increasesrelatively closer to the folding line FL, and the distance between thegrooves decreases relatively closer to the folding line FL. Accordingly,the foldability (or the ease of folding) of the plate 840 can beimproved. Similarly, the height (or average height) of the groovesdecreases relatively closer to the folding line FL. Accordingly, thefoldability of the plate 840 can also be improved.

Since the plate 840 is attached to the lower flexible module 230 via thedouble-sided adhesive film 850, the plate 840 may affect the control ofthe vertical position of a neutral plane NP of the foldable displaydevice 100_6. The vertical position of the neutral plane NP can becontrolled by adjusting the height of the grooves of the plate 840.

Although not specifically illustrated in FIG. 8, the foldable displaydevice 100_5 may further include the buffer film 471 of FIG. 4. Thebuffer film 471 may be interposed between the double-sided adhesive film850 and the plate 840.

FIG. 9 is a cross-sectional view of a foldable display device accordingto another embodiment of the invention.

Referring to FIG. 9, a foldable display device 100_6 substantiallydiffers from the foldable display device 100_5 of FIG. 8 in that itincludes a plate 940.

As described above with regard to the plate 840 of FIG. 8, the averageheight (or average thickness, volume, or area) of the plate 940 in afolding region FR may be relatively smaller than the average height (oraverage thickness, volume, or area) of the plate 940 in a non-foldingregion.

The plate 940 may include a groove formed on the bottom surface thereofto correspond to the whole folding region FR.

First corners C1 and second corners C2 of the groove of the plate 940may be rounded. Sidewalls S of the groove (i.e., sidewalls between thefirst corners C1 and the second corners C2) may be sloped.

The thickness of the groove of the plate 940 decreases relatively closerto a folding line FL and increases relatively closer to the firstcorners C1. The groove of the plate 940 may be generally semicircular inshape.

The plate 940, like the plate 840 of FIG. 8, may affect the control ofthe vertical position of a neutral plane NP of the foldable displaydevice 100_6.

Although not specifically illustrated in FIG. 9, the foldable displaydevice 100_6 may further include the buffer film 471 of FIG. 4. Thebuffer film 471 may be interposed between a double-sided adhesive film850 and the plate 940.

FIG. 10 is a cross-sectional view of a foldable display device accordingto another embodiment of the invention.

Referring to FIG. 10, a foldable display device 100_7 substantiallydiffers from the foldable display device 100_6 of FIG. 9 in that itincludes a plate 1040.

As described above with regard to the plate 940 of FIG. 9, the averageheight (or average thickness, volume, or area) of the plate 1040 in afolding region FR may be relatively smaller than the average height (oraverage thickness, volume, or area) of the plate 1040 in a non-foldingregion. The plate 1040 may include a groove formed on the bottom surfacethereof to correspond to the whole folding region FR.

First corners C1 and second corners C2 of the groove of the plate 940may be rounded. Sidewalls S of the groove (i.e., sidewalls between thefirst corners C1 and the second corners C2) may be sloped.

The thickness of the groove of the plate 1040 may be uniform from thefirst corners C1 to a folding line FL. That is, the inside of the grooveof the plate 1040 may be generally flat.

The plate 1040, like the plate 840 of FIG. 8, may affect the control ofthe vertical position of a neutral plane NP of the foldable displaydevice 100_7.

Although not specifically illustrated in FIG. 10, the foldable displaydevice 100_7 may further include the buffer film 471 of FIG. 4. Thebuffer film 471 may be interposed between a double-sided adhesive film850 and the plate 1040.

FIG. 11 is a cross-sectional view of a foldable display device accordingto another embodiment of the invention.

Referring to FIG. 11, a foldable display device 100_8 substantiallydiffers from the foldable display device 100_7 of FIG. 10 (or thefoldable display device 100_5 of FIG. 8) in that it includes a plate1140.

As described above with regard to the plate 1040 of FIG. 10, the averageheight (or average thickness, volume, or area) of the plate 1140 in afolding region FR may be relatively smaller than the average height (oraverage thickness, volume, or area) of the plate 1040 in a non-foldingregion. The entire bottom of the plate 1140 may be upwardly recessed inthe folding region FR.

In the folding region FR, the plate 1140, like the plate 840 of FIG. 8,may include grooves formed on the bottom surface thereof. The groovesmay be arranged in a left-to-right direction.

By adjusting the density and width of, and the distance between, thegrooves of the plate 1140, the foldability of the plate 1140 can beimproved.

Although not specifically illustrated in FIG. 11, the foldable displaydevice 100_8 may further include the buffer film 471 of FIG. 4. Thebuffer film 471 may be interposed between a double-sided adhesive film850 and the plate 1140.

FIG. 12 is a cross-sectional view of a foldable display device accordingto another embodiment of the invention.

Referring to FIG. 12, a foldable display device 100_9 substantiallydiffers from the foldable display device 100 of FIG. 2 in that itincludes first through fourth intermediate films 771 through 774 andfirst through sixth double-sided adhesive films 751 through 756.

The first through fourth intermediate films 771 through 774 may haveflexibility. The first through sixth double-sided adhesive films 751through 756, like the first double-sided adhesive film 251 of FIG. 2,may have adhesives on both the top surfaces and the bottom surfacesthereof.

The first intermediate film 771 may be disposed between a first plate241 and a lower flexible module 230. The third intermediate film 773 maybe disposed between the first plate 241 and the first intermediate film771. Similarly, the second intermediate film 772 may be disposed betweena second plate 242 and the lower flexible module 230, and the fourthintermediate film 774 may be disposed between the second plate 242 andthe second intermediate film 772.

The first double-sided adhesive film 751 may be disposed between thefirst intermediate film 771 and the lower flexible module 230. The firstdouble-sided adhesive film 751 may have substantially the same size (orarea) as the first intermediate film 771 and may completely overlap withthe first intermediate film 771. The third double-sided adhesive film753 may be disposed between the first and third intermediate films 771and 773, and the fifth double-sided adhesive film 755 may be disposedbetween the third intermediate film 773 and the first plate 241. Thethird and fifth double-sided adhesive films 753 and 755 may havesubstantially the same size (or area) as the third intermediate film 773and may completely overlap with the third intermediate film 773. Thus,the first plate 241 may be coupled to the lower flexible module 230 viathe first and third intermediate films 771 and 773 and the first, third,and fifth double-sided adhesive films 751, 753, and 755.

Similarly, the second double-sided adhesive film 752 may be disposedbetween the second intermediate film 772 and the lower flexible module230. The second double-sided adhesive film 752 may have substantiallythe same size (or area) as the second intermediate film 772 and maycompletely overlap with the second intermediate film 772. The fourthdouble-sided adhesive film 754 may be disposed between the second andfourth intermediate films 772 and 774, and the sixth double-sidedadhesive film 756 may be disposed between the fourth intermediate film774 and the second plate 242. The fourth and sixth double-sided adhesivefilms 754 and 756 may have substantially the same size (or area) as thefourth intermediate film 774 and may completely overlap with the fourthintermediate film 774. Thus, the second plate 242 may be coupled to thelower flexible module 230 via the second and fourth intermediate films772 and 774 and the second, fourth, and sixth double-sided adhesivefilms 752, 754, and 756.

The second intermediate film 772 may be disposed on substantially thesame plane as the first intermediate film 771 and may be a firstdistance L1 apart from the first intermediate film 771 in aleft-to-right direction. The second intermediate film 772 may besubstantially symmetrical with the first intermediate film 711 withrespect to a folding line FL.

The fourth intermediate film 774 may be disposed on substantially thesame plane as the third intermediate film 773 and may be a seconddistance L2 apart from the third intermediate film 773 in theleft-to-right direction. The fourth intermediate film 774 may besubstantially symmetrical with the third intermediate film 713 withrespect to the folding line FL.

The distance between the third and fourth intermediate films 773 and774, i.e., the second distance L2, may be relatively greater than thedistance between the first and second intermediate films 771 and 772,i.e., the first distance L1. Also, the first distance L1 may berelatively greater than the distance between first and second plates 241and 242, i.e., a third distance L3.

In this case, non-folding regions may be set as a region in which therigid film 240, the first and third intermediate films 771 and 773, andthe lower flexible module 230 all overlap with one another and a regionin which the rigid film 240, the second and fourth intermediate films772 and 774, and the lower flexible module 230 all overlap with oneanother. Accordingly, a folding region FR may be substantially definedby the third and fourth intermediate films 773 and 774, which are themost distant apart from each other and may be a region that does notoverlap with the third and fourth intermediate films 773 and 774 in thethickness direction.

The first and third intermediate films 771 and 773 may overlap with thefolding region FR, and the first intermediate film 771 (or the firstdouble-sided adhesive film 751) and the third intermediate film 773 (orthe second double-sided adhesive film 752) can contribute to theadjustment of the position of a neutral plane NP. Also, the first andthird intermediate films 771 and 773 can prevent the flexibility of thefoldable display device 100_9 from rapidly changing and can distributestress caused by bending at the boundaries between the folding region FRand the non-folding regions.

Although not specifically illustrated in FIG. 12, the foldable displaydevice 100_9 may include the first and second buffer films 471 and 472of FIG. 4. The first buffer film 471 may be disposed between the fifthdouble-sided adhesive film 755 and the first plate 241, and the secondbuffer film 472 may be disposed between the sixth double-sided adhesivefilm 756 and the second plate 242.

Although not specifically illustrated in FIG. 12, the foldable displaydevice 100_9 may further include the single-sided adhesive film 260 ofFIG. 1 or the first and second films 561 and 562 of FIG. 5. Thesingle-sided adhesive film 260 (or the first and second films 561 and562) may be disposed between the lower flexible module 230 and the firstplate 241, between the lower flexible module 230 and the second plate242, between the first intermediate film 771 and the first plate 241,and/or between the second intermediate film 772 and the second plate242.

FIGS. 13 through 23 are cross-sectional views of foldable displaydevices according to other embodiments of the invention.

Referring to FIG. 13, a foldable display device 100_10 substantiallydiffers from the foldable display device 100 of FIG. 2 in that it doesnot include the single-sided adhesive film 260.

In the foldable display device 100 of FIG. 2, the lower double-sidedadhesive film NAD2, the lower flexible module 230, and the single-sidedadhesive film 260 are provided to form the lower neutral planecontroller LNPC. On the other hand, in the foldable display device100_10 of FIG. 13, only the lower double-sided adhesive film NAD2 andthe lower flexible module 230 are provided to form the lower neutralplane controller LNPC.

Accordingly, non-folding regions may be substantially defined by firstand second double-sided adhesive films 251 and 252, and in a foldingregion FR, a neutral plane NP can be partially aligned with (or,partially located or positioned within) a display module 210.

Referring to FIG. 14, a foldable display device 100_11 substantiallydiffers from the foldable display device 100_10 of FIG. 13 in that itincludes a plate 1440.

The plate 1440 includes holes in a folding region FR. The holes may beformed to penetrate the plate 1440 in a thickness direction and may bearranged in series in a left-to-right direction. Although notspecifically illustrated in FIG. 14, in a folding region FR, the plate1440 may have a mesh structure in a plan view. Accordingly, there is noneed to form separate pores (or air passages connecting the gap betweenfirst and second double-sided adhesive films 251 and 252 and theoutside) in the plate 1440.

Referring to FIG. 15, a foldable display device 100_12 substantiallydiffers from the foldable display device 100_11 of FIG. 14 in that itincludes a plate 1540.

The plate 1540 may include grooves formed on the top surface and thebottom surface thereof. The grooves formed on the top surface of theplate 1540 may be arranged in a left-to-right direction. The groovesformed on the bottom surface of the plate 1540 may be arranged in theleft-to-right direction to be staggered with the grooves formed on thetop surface of the plate 1540. That is, in a cross-sectional view, theplate 1540 may have a zigzag pattern in the folding region FR.

Pores may be formed in the plate 1540.

Referring to FIG. 16, a foldable display device 100_13 substantiallydiffers from the foldable display device 100_12 of FIG. 15 in that itincludes a plate 1640.

As described above with regard to the plate 1140 of FIG. 11, the entirebottom of the plate 1640 may be upwardly recessed in a folding region FRand may include grooves. By adjusting the density and width of, and thedistance between, the grooves of the plate 1640, the foldability of theplate 1640 can be improved.

Pores may be formed in the plate 1540.

Referring to FIG. 17, a foldable display device 100_14 substantiallydiffers from the foldable display device 100_13 in that it includes aplate 1740.

As described above with regard to the plate 1140 of FIG. 11, the entirebottom of the plate 1640 may be upwardly recessed in a folding regionFR. The plate 1740, like the plate 1540 of FIG. 15, may include groovesformed on the top surface and the bottom surface thereof. In across-sectional view, the plate 1740, like the plate 1540 of FIG. 15,may have a zigzag pattern in the folding region FR.

Pores may be formed in the plate 1740.

Alternatively, the plate 1740 may include holes, instead of the groovesformed on both surfaces thereof, in the folding region FR and may have amesh structure in a plan view.

Referring to FIG. 18, a foldable display device 100_15 substantiallydiffers from the foldable display device 100_14 of FIG. 17 in that itincludes a plate 1840.

The plate 1840 may include a groove corresponding to a folding region FRon the top surface thereof. That is, in the folding region FR, theentire top of the plate 1840 may be downwardly recessed. Pores may beformed in the plate 1840.

Referring to FIG. 19, a foldable display device 100_16 substantiallydiffers from the foldable display device 100_15 of FIG. 18 in that itincludes a plate 1940.

The plate 1940 may include a groove corresponding to a folding region FRon the top surface thereof. Also, the plate 1940 may include groovesformed on the bottom surface thereof. The grooves may be arranged in aleft-to-right direction.

Pores may be formed in the plate 1940.

As described above with regard to the plate 1440 of FIG. 14, the plate1940 may include holes, instead of the grooves, in the folding region FRand may have a mesh structure in a plan view.

Referring to FIG. 20, a foldable display device 100_17 substantiallydiffers from the foldable display device 100_16 of FIG. 19 in that itincludes a plate 2040.

The plate 2040 may include a groove corresponding to a folding region FRon the top surface thereof. Also, the plate 2040 may include groovesformed on each of the top and bottom surfaces thereof. That is, in across-sectional view, the plate 2040 may have a zigzag pattern in thefolding region FR.

Although not specifically illustrated in FIG. 20, pores may be formed inthe plate 2040.

Referring to FIG. 21, a foldable display device 100_18 substantiallydiffers from the foldable display device 100_17 of FIG. 20 in that itincludes a plate 2140.

The plate 2140 may include a groove on each of the top and bottomsurfaces thereof. In a folding region FR, the top of the plate 2140 maybe downwardly recessed, and the bottom of the plate 2140 may be upwardlyrecessed. That is, the plate 2140 may have a substantial dumbbell shapein a cross-sectional view.

Although not specifically illustrated in FIG. 21, pores may be formed inthe plate 2140.

Referring to FIG. 22, a foldable display device 100_19 substantiallydiffers from the foldable display device 100_18 of FIG. 21 in that itincludes a plate 2240.

The plate 2240 has a substantial dumbbell shape in a cross-sectionalview. In a folding region FR, the plate 2240 may include grooves formedon the bottom surface thereof. The grooves may be arranged in aleft-to-right direction.

Pores may be formed in the plate 2240.

As described above with regard to the plate 1440 of FIG. 14, the plate2240 may include holes, instead of the grooves, in the folding region FRand may have a mesh structure in a plan view.

Referring to FIG. 23, a foldable display device 100_20 substantiallydiffers from the foldable display device 100_19 of FIG. 22 in that itincludes a plate 2340.

The plate 2340 has a substantial dumbbell shape in a cross-sectionalview. In a folding region FR, the plate 2340 may include grooves formedon each of the top and bottom surfaces thereof. That is, in across-sectional view, the plate 2340 may have a zigzag pattern in thefolding region FR.

Although not specifically illustrated in FIG. 23, pores may be formed inthe plate 2340.

The effects of the invention are not limited by the foregoing, and othervarious effects are anticipated herein.

Although certain embodiments and implementations have been describedherein, other embodiments and modifications will be apparent from thisdescription. Accordingly, the inventive concepts are not limited to suchembodiments, but rather to the broader scope of the appended claims andvarious obvious modifications and equivalent arrangements as would beapparent to a person of ordinary skill in the art.

What is claimed is:
 1. A foldable display device assembly, comprising: arigid film having first and second sections spaced apart from eachother, the rigid film being foldable about a folding axis disposedbetween the first and second sections of the rigid film; an adhesionstructure having first and second adhesion sections spaced apart fromeach other, the first and second adhesion sections being disposed on thefirst and second sections of the rigid film, respectively; a lowerflexible module disposed on the adhesion structure; a flexible displaymodule disposed on the lower flexible module; and an upper flexiblemodule disposed on the flexible display module, wherein at least aportion of a lower surface of the first adhesion section corresponds toa first lower adhesion region to which an upper surface of the firstsection of the rigid film is adhered, at least a portion of an uppersurface of the first adhesion section corresponds to a first upperadhesion region to which a lower surface of the lower flexible module isadhered, and an is area of the first lower adhesion region issubstantially different from an area of the first upper adhesion region,wherein at least a portion of a lower surface of the second adhesionsection corresponds to a second lower adhesion region to which an uppersurface of the second section of the rigid film is adhered, at least aportion of an upper surface of the second adhesion section correspondsto a second upper adhesion region to which a lower surface of the lowerflexible module is adhered, and an area of the second lower adhesionregion is substantially different from an area of the second upperadhesion region.
 2. The foldable display device assembly of claim 1,wherein the lower flexible module continuously extends over the firstand second sections of the rigid film.
 3. The foldable display deviceassembly of claim 2, wherein a distance between the first and secondlower adhesion regions is substantially greater than a distance betweenthe first and second sections of the rigid film.
 4. The foldable displaydevice assembly of claim 3, wherein the entire upper surface of thefirst adhesion section and the entire upper surface of the secondadhesion section are adhered to the lower surface of the lower flexiblemodule.
 5. The foldable display device assembly of claim 4, wherein thedistance between the first and second lower adhesion regions issubstantially greater than a distance between the first and second upperadhesion regions.
 6. The foldable display device assembly of claim 2,wherein a distance between the first and second upper adhesion regionsis substantially greater than a distance between the first and secondsections of the rigid film.
 7. The foldable display device assembly ofclaim 6, wherein the entire lower surface of the first adhesion sectionand the entire lower surface of the second adhesion section are adheredto the upper surface of the first section of the rigid film and theupper surface of the second section of the rigid film, respectively. 8.The foldable display device assembly of claim 7, wherein a distancebetween the first and second lower adhesion regions is substantiallygreater than a distance between the first and second sections of therigid film.
 9. The foldable display device assembly of claim 1, whereinthe lower flexible module has a substantially lower light transmittancethan the upper flexible module.
 10. A foldable display device assembly,comprising: a plate having a first section, a second section, and aconnection section connected between the first and second sections, theplate being foldable about a folding axis disposed between the first andsecond sections, the first and second sections being rigid orsemi-rigid, the connection section having a foldability and a firstwidth measured in a direction from the first section of the plate to thesecond section of the plate when the foldable display device assembly isunfolded; a lower flexible module disposed on the plate; a firstdouble-sided adhesive film disposed on the lower flexible module; aflexible display module disposed on the first double-sided adhesivefilm, the flexible ii display module having an electroluminescent unit;a second double-sided adhesive film disposed on the flexible displaymodule; and an upper flexible module disposed on the second double-sidedadhesive film, wherein the connection section of the plate has anaverage thickness substantially is smaller than the first and secondsections of the plate, and the lower flexible module has a substantiallylower light transmittance than the upper flexible module.
 11. Thefoldable display device assembly of claim 10, further comprising a thirddouble-sided adhesive film disposed between the plate and the lowerflexible module, wherein the third double-sided adhesive film extendscontinuously over the first and second sections of the plate.
 12. Thefoldable display device assembly of claim 11, wherein a neutral planehaving a width substantially smaller than the first width issubstantially symmetrical with respect to the folding axis when thefoldable display device assembly is folded or unfolded, and the thirddouble-sided adhesive film at least in part locates the neutral planewithin a foldable region of the flexible display module.
 13. Thefoldable display device assembly of claim 10, wherein the connectionsection of the plate has a portion having an average thicknessdecreasing in the direction in which the first width is measured. 14.The foldable display device assembly of claim 10, wherein the connectionsection of the plate has a downwardly opening recess.
 15. The foldabledisplay device assembly of claim 14, wherein the downwardly openingrecess has at least one of a rounded inner corner and/or a rounded outercorner.
 16. The foldable display device assembly of claim 14, whereinthe connection section of the plate has an upwardly opening recess. 17.The foldable display device assembly of claim 16, wherein the upwardlyopening recess has a rounded inner corner.
 18. The foldable displaydevice assembly of claim 10, wherein the connection section of the platehas an upwardly opening recess.
 19. The foldable display device assemblyof claim 18, wherein the upwardly opening recess has a rounded innercorner.
 20. The foldable display device assembly of claim 10, whereinthe connection section of the plate has a plurality of holes.
 21. Thefoldable display device assembly of claim 10, further comprising a thirddouble-sided adhesive film disposed between the plate and the lowerflexible module, wherein the third double-sided adhesive film comprisesthird and fourth sections separated from each other, the third sectionof the third double-sided adhesive film is disposed between the firstsection of the plate and the lower flexible module, and the fourthsection of the third double-sided adhesive film is disposed between thesecond section of the plate and the lower flexible module.
 22. Thefoldable display device assembly of claim 10, further comprising: abuffer film disposed on the plate; and a third double-sided adhesivefilm disposed between the buffer film and the lower flexible module,wherein the buffer film prevents an adhesion between the thirddouble-sided adhesive film and the plate from decreasing due to adifference in a physical property between the plate and the thirddouble-sided adhesive film.
 23. The foldable display device assembly ofclaim 22, wherein the buffer film includes a non-metallic inorganicmaterial.
 24. The foldable display device assembly of claim 23, whereinthe non-metallic inorganic material includes silicon.
 25. The foldabledisplay device assembly of claim 23, wherein the plate includes a metal,and the third double-sided adhesive film includes an organic material.26. A foldable display device assembly, comprising: a rigid film havingfirst and second sections between which a space having a width measuredin a direction from the first section of the rigid film to the secondsection of the rigid film when the foldable display device assembly isunfolded is disposed, the rigid film being foldable about a folding axisdisposed between the first and second sections; a buffer film disposedon the rigid film; a first double-sided adhesive film disposed on thebuffer film; a lower flexible module disposed on the first double-sidedadhesive film; a second double-sided adhesive film disposed on the lowerflexible module; a flexible display module disposed on the seconddouble-sided adhesive film, the flexible display module having anelectroluminescent unit; a third double-sided adhesive film disposed onthe flexible display module; and an upper flexible module disposed onthe third double-sided adhesive film, wherein the lower flexible modulehas a substantially lower light transmittance than the upper flexiblemodule, and the buffer film prevents an adhesion between the rigid filmand the first double-sided adhesive film from decreasing due to adifference in a physical property between the rigid film and the firstdouble-sided adhesive film.
 27. The foldable display device assembly ofclaim 26, wherein the buffer film includes a non-metallic inorganicmaterial.
 28. The foldable display device assembly of claim 27, whereinthe non-metallic inorganic material includes silicon.
 29. The foldabledisplay device assembly of claim 27, wherein the plate includes a metal,and the first double-sided adhesive film includes an organic material.